Micrographs of Precipitation Nozzles

Discussion in 'Silver Gelatin Based Emulsion Making & Coating' started by holmburgers, Jan 26, 2013.

  1. holmburgers

    holmburgers Member

    Messages:
    4,423
    Joined:
    Aug 13, 2009
    Location:
    Rochester NY
    Shooter:
    Multi Format
    Howdy all,

    One of the perks of being at GEH is the conservation lab. Not only do they have a bunch of awesome microscopes, but they have people that know how to use them!

    Mark Osterman brought in a couple of old Polaroid precipitation nozzles (needles for introducing silver-halide into the emulsion pot) and I wondered how big the openings were. I asked Ralph Wiegandt if he could measure them somehow and he showed me how to do it on the microscope. These are at 50x.

    There are 3 images; two metal nozzles that were originally used by Polaroid and a glass nozzle, hand pulled by Mark that we use in the emulsion lab here at GEH. The metal ones measure 0.6mm and 1.2mm; the glass one is also (miraculously) 0.6mm.

    In hypodermic needle gauges, this translates to 16g and 21g.

    To me, this brings up an interesting quandary. The same quantity of silver-solution can be introduced into the gel/halide "pot" in a set amount of time, yet the nozzles can be bigger or smaller. The effect being, to increase the pressure at which solution enters the pot.

    On one hand you can have an incredibly fine stream of high pressure going through a very small nozzle, and on the other hand you can imagine a large nozzle that just "drips" out.

    So how important is the nozzle size and the pressure?, or is rate of addition the more important factor??
     

    Attached Files:

  2. dwross

    dwross Subscriber

    Messages:
    1,002
    Joined:
    Feb 13, 2004
    Location:
    Oregon Coast
    Shooter:
    Multi Format
    Hi Chris,

    Nice to see you again. Good to see you're having so much fun at GEH!

    re: "So how important is the nozzle size and the pressure?, or is rate of addition the more important factor??"

    It's hard to imagine all the alchemy and uber engineering that was engaged in to make Polaroid products, but this film, http://thelightfarm.com/cgi-bin/showvideo.py, starting at 7:56 minutes gives an idea of how important extreme precision was to Kodak, not all that long ago. (Spoiler alert: NOT :smile:)

    d
     
  3. AgX

    AgX Member

    Messages:
    11,904
    Joined:
    Apr 5, 2007
    Location:
    Germany
    Shooter:
    Multi Format
    A "jet" compared to a "drop" delivering both the same flux (volume per time) would have a larger surface.
     
  4. holmburgers

    holmburgers Member

    Messages:
    4,423
    Joined:
    Aug 13, 2009
    Location:
    Rochester NY
    Shooter:
    Multi Format
    Haha, wow Denise, you're not kidding. There's no way they were really making film like that by that point... right?? :wink: I didn't quite realize what all went into getting that film translated; what a great service you guys did in doing so!

    A "jet" would also reach further into the solution and produce much more turbulence on its journey. I posed this question to Ron and he said that a high pressure jet will remain "cohesive" (I believe this is the word he used...?) longer and thus delay the reaction slightly. But on the other hand there is more surface area, and you'd have to think that the turbulence that it encounters would also aid in quick mixing.

    Who knows though; it's all arm-chair emulsion making at this point. It'd be nice to make the same emulsion with a "drip" and a "jet", with the same total rate of addition, and compare the two.
     
  5. Hexavalent

    Hexavalent Subscriber

    Messages:
    577
    Joined:
    Nov 19, 2009
    Location:
    Ottawa, Onta
    Shooter:
    Multi Format
    I use 24 gauge needles, directed as closely as possible to the stirrer. So far, I've never had any "crunchies" or pepper grain, except when I once used a larger bore needle. 24 ga. and finer does require quite a bit of pressure for quick delivery!
     
  6. holmburgers

    holmburgers Member

    Messages:
    4,423
    Joined:
    Aug 13, 2009
    Location:
    Rochester NY
    Shooter:
    Multi Format
    Very interesting Ian; that's quite a fine nozzle indeed. How large of a bore are you referring to when you mention the crunchies??

    You bring up a good point about delivery; a high pressure nozzle would make a long addition easier and more consistent, compared to low pressure where the accuracy of delivery is all controlled by your muscles. With high pressure you kinda just 'give it hell' and it ejects as fast as it can. We've been using Mark O's bulb thingy which works on that principle; you squeeze it 100% and the rate is more or less controlled by the constant pressure you've created in the system.

    And then there's this option (warning: eye candy)...
     
  7. Hexavalent

    Hexavalent Subscriber

    Messages:
    577
    Joined:
    Nov 19, 2009
    Location:
    Ottawa, Onta
    Shooter:
    Multi Format
    Chris, the larger bore item was one of those hardware store syringe thingy designed for glue, probably 1mm. It was very tricky to achieve a steady delivery. Basically useless.
     
  8. kb3lms

    kb3lms Subscriber

    Messages:
    872
    Joined:
    Jun 24, 2006
    Location:
    Reading, PA
    Shooter:
    35mm
    I 've made myself a hand crank syringe pump and use 18 gauge needles and nylon (I think) tubing. The tubing came from empty hair spray bottles. It's not really not that hard to control delivery rate. Below is a picture.

    [​IMG]

    The tubing arrangement is likely to change a little because the clothespin tends to move around on the side of the pot and the tubes don't really point were I want them to. Also, been thinking about changing to a smaller sized needle.

    I think the part about the cohesiveness Ron mentioned to you is that the high pressured streams push away the other liquids and allow the salt and silver reactants to combine at a more closely controlled ratio. So, the crystals are nucleated within the stream and then carried away into the rest of the emulsion. You want to have the reactants introduced sub-surface.
     

    Attached Files:

  9. Orioes

    Orioes Member

    Messages:
    6
    Joined:
    Jul 22, 2012
    Shooter:
    35mm
    Wow, you know I knew mass production of film was a major industrial undertaking and it was in its time the largest consumer of silver but that never really hit home till I saw the office building sized film base machine or the guy shoveling in silver ingots by the gross. Very cool movie.
     
  10. holmburgers

    holmburgers Member

    Messages:
    4,423
    Joined:
    Aug 13, 2009
    Location:
    Rochester NY
    Shooter:
    Multi Format
    I see what you mean Ian; it does seem like one would need a little back pressure to get a steady delivery.

    Jason, wow, that's great! Just this week the idea of syringe pumps hit me, but it's great to know that others have already been thinking about this stuff.

    I've been mulling over a design in my head... imagine that the syringe (or pump) is seated on the counter, next to the kettle, with a length of plastic tubing leading to a hypodermic needle which is held in position over the pot by a lab stand. The stand could clamp a cork, through which you push the needle.

    Regarding an 18-gauge needle; this is the size that seemed like a good fit to me, but I haven't used it in practice. I'd be very curious to know why you might be looking for something smaller; was it not ideal?

    I was able to find some 18g needles in 4" length, which seems like a good length to work with. (here)
     
  11. kb3lms

    kb3lms Subscriber

    Messages:
    872
    Joined:
    Jun 24, 2006
    Location:
    Reading, PA
    Shooter:
    35mm
    Chris,

    Good find on the needles on MedVet. I have bought plenty of syringes from them but never looked for needles, although I have only purchased the non-sharp type dispensing tips to date. And, I really don't want sharps laying around.

    As for your idea of needles through a cork, you could do that. As you can see, mine works by attaching the needles to the syringe and the tubing leads to the kettle with the needles acting as an adapter for the tubing . The tubes are held to the kettle with a clothespin. The syringe pump sits on a stand (aka brick) next to the water bath (aka temperature controlled crock pot). So, in a sense, my pump is not really injecting with much pressure at all.

    What you want to happen is that the liquid is injected subsurface and that you get all of the chemical out of the syringe and the line since AgNO3 is not cheap. If you are trying double jet, you want the reactants injected next to each other and I have seen some diagrams that even show an outer shield around the tubes or needles to allow the reactants to mix in a sheltered area.

    Another thing I have found is that AgNO3 is building up in the stainless needle on the silver side. Actually it almost looks like metallic silver. I don't know if this is a conditioning effect or I should clean it out.

    Mine is set up for double-jet, obviously, but I may "step back" to SRADs for a bit. DJ emulsions have shown to be kind of touchy in terms of finishing. I am guessing that in being more monodisperse, when things go wrong in terms of fog, it goes bad very fast, where a polydisperse emulsion gives a little more room for error. That's why I haven't mentioned anything about making DJ emulsions - I haven't made a good one yet without a lot of fog, although they do work. And no, so far, they aren't higher speed but they have been somewhat higher contrast.

    I am thinking about a smaller than 18 gauge needle and tubing in order to get a higher pressure jet but I don't think it will make a night and day difference to the results. Maybe your design idea is what I am really looking for. But, how do you attach the tubing to the needle?

    -- Jason
     
  12. AgX

    AgX Member

    Messages:
    11,904
    Joined:
    Apr 5, 2007
    Location:
    Germany
    Shooter:
    Multi Format
    Sharp needle tips can be grinded flat. Best done with a micro-drill and a cutting disk.
     
  13. JOSarff

    JOSarff Member

    Messages:
    203
    Joined:
    Mar 5, 2008
    Location:
    Santa Fe, NM
    Shooter:
    8x10 Format
    Jason:

    I think it's just Silver plating onto the stainless steel of the needle. If the Silver deposit in the needle is reducing the flow then I would suggest soaking the needle in a silver solvent such as Sodium or Ammonium Thiosulfate (Fixer).

    There are adapters made that are female luer-lok to tubing and tubing to male luer-lok. The male luer-lok connection is where you attach the needle and place in the kettle. These may be available from the Vet supply Co. Chris mentioned earlier or eBay..

    All the best,

    Joe
     
    Last edited by a moderator: Jan 28, 2013
  14. Sponsored Ad
  15. dwross

    dwross Subscriber

    Messages:
    1,002
    Joined:
    Feb 13, 2004
    Location:
    Oregon Coast
    Shooter:
    Multi Format
    Silver plating is always a nuisance to keep in mind. Happens with glass stopcock burets, too. It's important to keep things rinsed out. I assume the reason to go with such elaborate tools as hypodermic needles is the hope that they will give you extreme precision (??). It sounds more like a set-up for spurious precision. I know that sounds like a harsh buzz-kill, but if there's even a little bit of gunk in a hypodermic, the changes in rate of delivery and the turbulence will seriously throw off your results. K.I.S.S.
     
  16. Hexavalent

    Hexavalent Subscriber

    Messages:
    577
    Joined:
    Nov 19, 2009
    Location:
    Ottawa, Onta
    Shooter:
    Multi Format
    Gunk in the hypodermic? I wouldn't use a needle twice for any purpose :smile:
     
  17. Photo Engineer

    Photo Engineer Subscriber

    Messages:
    25,771
    Joined:
    Apr 19, 2005
    Location:
    Rochester, NY
    Shooter:
    Multi Format
    The mixing rate of a solution being added is dependent on flow rate, mixer speed, point of entry and solution concentration among a few of the variables.

    A very concentrated solution can maintain its integrity for quite some time unless the stream is broken up by the mixer and even baffles which introduce turbulence to assist in breaking up bands or "tubes" of added solution. Imagine squeezing a tube of toothpaste into water. If you do it in a continuous stream you get a "tube" of paste in water. If you do it "somehow" in chunks, you get "drops" of toothpaste. It is the job of the designer to break up these pieces of whatever nature, in such a way as to achieve a good mix.

    Now, our problem with Silver Nitrate is not as bad as using toothpaste but the analogy exists and if you add concentrated AgNO3 solution to water, you can actually see the "tubes" or "drops" and they vary with concentration, rate of addition and diameter or size of drop or tube.

    You can experiment with this, as I did, with concentrated table salt or the like, with dye in it, added to plain water at varying rates, with different mixing and etc. This will "teach" you the optimum for any condition.

    I get turkey basters at Home Depot, and I get large size (80 ml) from the Formulary. All of the tips have Luer connectors and I can exchange tips.

    Expect some corrosion with cheap stainless. I try to stay with non-magnetic, non-plated parts, but this is not always possible. So, when things corrode I replace them. Oh, and standard tubing goes over a Luer male connector on a syringe and can be cut to any length and clipped in any position. I have shown pictures of that here on APUG.

    PE
     
  18. holmburgers

    holmburgers Member

    Messages:
    4,423
    Joined:
    Aug 13, 2009
    Location:
    Rochester NY
    Shooter:
    Multi Format
    Yes Jason, I'm amazed you are already going after double run emulsions; I figure there's enough to keep me occupied with SR and SRADs for a long time.. :smile: If you had a labstand and clamp like this (please don't spend this much money though...), you could easily hold a cork and mount the needle in that.

    Unfortunately those MedVet needles are sharp; I thought they were blunt for some reason. It seems that grinding them down shouldn't be a nuisance.

    The silver plating shouldn't be a problem, as Joe said, and as long as you flush your hypodermic needles with hot water after use and allow to dry, I can't foresee any "gunk" being a problem. The only thing that's going through it is silver-nitrate & water. I doubt that hypo will get rid of it since it's metallic silver though, which has effectively "printed out".

    I honestly can't think of a more simple solution than hypodermic needles with standardized sizes. It's not about uber-precision per se, but about having a specific orifice that gives you the right "ejection" qualities; powerful stream, good back pressure, accurate placement in kettle. They're cheap and I also think that if you have the right s.s. needle, you should be able to reuse it as long as you want... but IDK.

    Ron, with a simple magnetic-stirrer, would you ideally want the stream of AgNO3 to go right into the most turbulent zone, near the stirrer?
     
  19. kb3lms

    kb3lms Subscriber

    Messages:
    872
    Joined:
    Jun 24, 2006
    Location:
    Reading, PA
    Shooter:
    35mm
    Yep, that's me. I had to try it. When I sit here at work waiting for the code to build or one of those "endless" meetings, well, you kind of zone out sometimes and ...

    Yeah, don't be in a hurry. As PE has told us, there is more to this than meets the eye. Not that making a double-run is that hard, mind-you, but there are so many variables involved that it is hard to be able to tell what you might be doing. Eventually, though, over the long term it is probably the way forward.

    I noticed the buildup after my last double run. I've made three. Two worked, in that I got a working emulsion although it wasn't anything special. One was an outright failure, except I can use it for coating practice. Fortunately, they were all quite small. The needle should clean out easily enough, and if it doesn't, they are pretty inexpensive.

    No, not really. I was looking for two things, a smaller orifice to help slow down the flow rate thereby making it easier to add reactants over, say, a 20 minute period in a relatively constant stream. And second, as a way to bring the entry point of the reactants into proximity for mixing purposes. The first they achieve, the second they do not. The initial idea was to bend the needles to bring them together, but that doesn't work because you cannot bend them, or at least not easily without breaking them. So the idea switched to using tubing. I think Chris' idea is better than mine, though.

    Will have to look for this sort of tubing. Sounds like a solution.

    Another possible solution but will have to find tubing of the right size. I would guess it's available but never looked.

    Things on the photography front at my house have had to take a back seat lately. My available time has mostly been spent playing with the Mamiya 645 so have a little time to figure out the next steps.

    -- Jason
     
  20. kb3lms

    kb3lms Subscriber

    Messages:
    872
    Joined:
    Jun 24, 2006
    Location:
    Reading, PA
    Shooter:
    35mm
    Had a minute this afternoon to look for these. Search "Luer Fitting" on Amazon or eBay. There's all kinds available with barbs for all kinds of tubing.

    Thanks for the tip, Joe
     
  21. Photo Engineer

    Photo Engineer Subscriber

    Messages:
    25,771
    Joined:
    Apr 19, 2005
    Location:
    Rochester, NY
    Shooter:
    Multi Format
    A few comments are in order here.

    Mixing problems go way way up with RS (Run Salt - or Double Run) emulsion makes because the rate, position etc, become more critical. As a note here, with SR and SRAD, I have found little effect on the position of the entry point. With RS makes there is a problem.

    We used tubing. We had a plate with holes in it that the tubing went into, and this positioned them at the right place. For back pressure, we used glass or metal constrictors (like the tips on all plastic syringes with a feeding tip on them). These constrictors evened out the flow. There is a demo of this on the second DVD that I made, but it is very simple.

    Baffles were used to INCREASE turbulence, and we did NOT want to decrease turbulence. Go back to my toothpaste example and you will see what I mean, or look at the mixer photos I posted here about a year ago.

    PE
     
  22. Kirk Keyes

    Kirk Keyes Member

    Messages:
    3,268
    Joined:
    Jun 17, 2004
    Location:
    Portland, OR
    Shooter:
    4x5 Format
    Nice!

    Since I've worked in analytical chemistry labs, I have experience with peristaltic pumps.

    From Wikipedia: A peristaltic pump is a type of positive displacement pump used for pumping a variety of fluids. The fluid is contained within a flexible tube fitted inside a circular pump casing (though linear peristaltic pumps have been made). A rotor with a number of "rollers", "shoes", "wipers", or "lobes" attached to the external circumference of the rotor compresses the flexible tube. As the rotor turns, the part of tube under compression is pinched closed (or "occludes") thus forcing the fluid to be pumped to move through the tube. Additionally, as the tube opens to its natural state after the passing of the cam ("restitution" or "resilience") fluid flow is induced to the pump. This process is called peristalsis and is used in many biological systems such as the gastrointestinal tract. Typically, there will be two or more rollers, or wipers, occluding the tube, trapping between them a body of fluid. The body of fluid is then transported, at ambient pressure, toward the pump outlet. Peristaltic pumps may run continuously, or they may be indexed through partial revolutions to deliver smaller amounts of fluid.

    They have a nice animation the Wikipedia page in case you are a visual person... http://en.wikipedia.org/wiki/Peristaltic_pump

    I think peristaltic pumps work better for this type of application, especially for flows in the 1 ml or so per minute range compared to syringe pumps. The stepper motor in a syringe pump is not running continuously, so it's constantly squirting out little bits of fluid, like a discrete automotive fuel injection system (not a CIS system) or like a ink jet printer. Little drops, not continously, over time. Also, a peristaltic pump is not limited by the size of the syringe. (Although you can replace the syringe in a syringe pump to get volumes larger than what 1 syringe can hold.)

    A peristaltic pump has a motor that runs in a much smoother fashion, and it is constantly pushing liquid out. You control the flow in a peristaltic pump by varying the motor speed and the diameter of the pump tubing. You can get a pretty wide range of flow from a peristatlic pump depending on the setup, from 0.001 ml/minute to hundreds of mls per minute. It just depends on the model of pump, the speed, and the tubing size.

    Here's some photos of the set-ups I had been working on a couple years ago:

    First Photo -
    This set-up for a single channel pump. The stirplate has a built-in heater, and there is a temp controller (reading 41C mounted onto a ring stand that attaches to the back of the hot plate. Also attached to the ring stand, is a clamp that hold a stainless tube that I have a thinner teflon tube inserted through and then the bottom end goes into the solution in the beaker.

    That teflon tube is connected to a silicone peristaltic pump tube by merely inserting the teflon tube into the silicone pump tube. The other end of the silicone pump tube goes into the graduated cylinder which is holding the silver nitrate solution.

    The 3rd thing in the beaker is a kitchen temp meter (the one with the right-angel bend at the top) and you can see it reads 40C on its display.

    I use a large, X-shaped, teflon-coated stirbar to get as much turbulance and mixing as posible.
    Peristaltic_Pump_Setup_for_Emulsion_Making-03200.JPG


    Second photo -
    Here's a close-up of the beaker and pump. You can see the end of the teflon tube that goes through the stainless tube. The stainless tube is just to hold the thin trflon tube. (I think the teflon is 24 or 28 ga. I have some that goes down to 36 ga. but I never tried it.) Since the teflon tube that thin is not stiff at all, it needed something for support. I had the stainless tube sitting around, so I used that. Otherwise, I would have taken some glass tubing and used it. I preferred the stainless as I didn't have to worry about breaking it!

    You can see the teflon coming down from the end of the stainless tube (off frame to the top) and into the polyvinylchloride peristaltic pump tube, which is a larger diameter. The little teflon tube is just butt-connected to the larger pump tubing merely by pressing it into the pump tube. If the difference in size between the two tubes is too great to do this, an intermediate size of pump tube can be used to go between the bigger and smaller tubes. No fittings are required using this technique.

    You can see the little lever on the pump platten that is used to apply pressure to the tube to firmly bring it into contact with the pump rollers. This pump has 8 rollers, which will give a smoother flow than a pump that uses say 2 rollers.
    Peristaltic_Pump_Setup_for_Emulsion_Making-03186.JPG


    Below - The tip of the dual solution nozzle. The tubing is 24 or 28 ga teflon tubing. One of the tubes is inserted into a long stainless tube for rigidity, the second teflon tube is strung on the outside of the stainless tube. They are held in place with short sections of PVC tubing, a smaller one to keep the teflon tube that's inside the stainless from pulling up into the stainless tube, and a larger one around the stainless tube and the second teflon tube.

    Note that the teflon tubes have very small opening. I have them mounted so that they are as close to each other as I can get them. They are also open perpendicular to the flow of the liquid past them to get the liquid to shear off the tip of the nozzles so the solutions get dispirsed into the make as quickly as possible.
    Peristaltic_Pump_Setup_for_Emulsion_Making-04631.JPG


    Below - Peristaltic pump set-up with two pump channels bring used. One for silver nitrate, the other for halide. You can see there pump nozzle in the beaker and behind it is the temp probe for the stirring hotplate. The two channels are loaded into the peristaltic pump, the close one has the platten for the pump tube tightened down so the liquid would flow, and back one has the platten loose to the pump is not flowing in that channel.

    Note the hemostat is being used to pinch the back pump tube shut so it does not siphon liquid out of the beaker! To put the back pump into operation, all that needs to be done is flip the plastic lever on the platten down and to the left to tighten the platten against the pump tube and release the hemostat.
    Peristaltic_Pump_Setup_for_Emulsion_Making-04649.JPG


    Below - The full setup in the darkroom. Red LED lights with rubylith over them just because... Laptop with rubylith of the screen - spreadsheet with all calcs and times for the make pulled up so it can bee seen and consulted during the run (and to play music - I was in there for hours...) Clipboard to make notes and record timing/addition times. Stirplate with temp controller, peristaltic pump, reagents prepped in plastic cups, darkroom timer running in 24 hr clock mode so I could easily see and record times.
    Peristaltic_Pump_Setup_for_Emulsion_Making-04647.JPG
     
  23. Photo Engineer

    Photo Engineer Subscriber

    Messages:
    25,771
    Joined:
    Apr 19, 2005
    Location:
    Rochester, NY
    Shooter:
    Multi Format
    Very nice Kirk. Similar to what I am now using except for the brand names on the equipment. That tubing pair being held together is pretty much what we did at EK and what I was describing above.

    Best wishes.

    PE
     
  24. Kirk Keyes

    Kirk Keyes Member

    Messages:
    3,268
    Joined:
    Jun 17, 2004
    Location:
    Portland, OR
    Shooter:
    4x5 Format
    PE - Well I came up with the nozzle config based on our discussions, so I'm glad it is close to what you were telling me.

    I forgot to mention that with the pump running at about a 1 ml/minute, it will squirt a pretty steady stream of liquid out the tip of the nozzle and across the lab bench due to the small inside diameter of the teflon tubing! Doing that is actually a great way to see how constant the pump pressure is.

    Also, I bought a lot of tubing (both teflon/ptfe and stainless) from smallparts.com. I see they are part of Amazon now...
     
  25. Photo Engineer

    Photo Engineer Subscriber

    Messages:
    25,771
    Joined:
    Apr 19, 2005
    Location:
    Rochester, NY
    Shooter:
    Multi Format
    Kirk;

    Good to see you here again. Hope things are well with you and your family.

    Yes, that squirt is quite "evil" if it gets away from you. I demo my pump on the DVD with a small tip and show how beaded drops become a rather hefty stream with just a tiny tip and the added backpressure. I wish I could put some video up on APUG, but there is no facility for it, and I don't feel like "donating" the footage to youtube.

    I am working on double runs and they are not easy. I have one that runs for over 3 hours, but so far it is too messy for the average person. It would challenge a big lab I think.

    PE
     
    Last edited by a moderator: Jan 30, 2013
  26. holmburgers

    holmburgers Member

    Messages:
    4,423
    Joined:
    Aug 13, 2009
    Location:
    Rochester NY
    Shooter:
    Multi Format
    Brilliant stuff; Kirk's setup is top notch.